It depends on the significance of what they know about you that could hurt you. It may result in your arrest, may hurt your feelings, it may hurt your marriage, it may hurt your career or it may simply embarrass you. It's very hard to say without the details.
Someone who betrays their country is called a traitor
When someone betrays you, how do you react.
Her
someone who betrays their party they are affiliated with.
when you get stabbed in the back it is when someone betrays you
A traitor
A bewrayer is a person who betrays someone else, or who divulges information to someone else.
it means a person who betrays someone else or a backstabber
A fryd is someone who betrays their lord or King. The word 'fryd' comes from fraud.
karma apparently
A person who betrays is a traitor or a turncoat. A person who betrays another is also called a Judas.
Verräter refers to someone who betrays another. Betrüger refers to someone who tricks or maliciously misleads someone else.